1. Field of the Invention
The present invention relates to an on-vehicle radar device, which is installed on a vehicle and obtains information about objects around the vehicle and also relates to a vehicle control system, which performs a vehicle control operation based on the information obtained by the on-vehicle radar device.
2. Description of Related Art
A traffic accident may occur in the following situations. For instance, a country where drivers keep to the right side of the road, it could happen that when a vehicle approaches an intersection to make a left turn, the driver of that vehicle is surprised with an oncoming straight-through vehicle that has suddenly appeared from a blind spot of an oncoming left turn vehicle, which is about to make a left turn at a center of the intersection (hereinafter, simply referred to as a left turn vehicle). Also, it could happen that when a vehicle is traveling straight on a street, a driver of that vehicle is surprises with a crossing vehicle that has suddenly appeared from a blind spot of a non-moving vehicle, which is parked on the side of the street (hereinafter, simply referred to as the non-moving vehicle). In the above cases, a collision could happen between the two approaching vehicles in the worst scenario. In view of this, it is desirable to have a technique that provides information about a state in the blind spot of the left turn vehicle or of the non-moving vehicle.
Furthermore, when a preceding vehicle ahead of a compact vehicle is a large vehicle, a view of the driver of the compact vehicle is largely masked by the large preceding vehicle, so that the driver of the compact vehicle cannot recognize a state ahead of the large preceding vehicle. As a result, for instance, when the driver of the large preceding vehicle suddenly applies the brakes, the drive of the compact vehicle cannot react with it, thereby possibly resulting in the collision. In view of the above situation, it is desirable to have a technique that provides information about a state in the blind spot of the preceding vehicle.
Particularly, information about a vehicle in front of the preceding vehicle ahead of the own vehicle is important in an adaptive cruise control (ACC) or a precrash safety system (PCS) at the time of correctly estimating a behavior (an acceleration or a deceleration) of the vehicle in front of the preceding vehicle to smoothly control the speed of the own vehicle.
In view of this, a drive assist system has been proposed to address the above disadvantage. In this system, sensors and/or cameras are arranged at specific points (e.g., intersections and curves of roads) to obtain information at these points. The information, which is obtained through the sensors and/or the cameras, is transmitted to a vehicle, which passes through these points, via communication devices arranged at these points, so that the driver of the vehicle can obtain the information of these points.
For example, Japanese Unexamined Patent Publication No. 2005-11249 discloses such a technique. According to this disclosed technique, when the own vehicle approaches an intersection and is about to make a left turn, the own vehicle obtains information about oncoming vehicles through the corresponding communication device. For instance, when a straight-through oncoming vehicle approaches the intersection, a voice warning is provided to the driver of the own vehicle.
Furthermore, Japanese Unexamined Patent Publication No. 10-000989 teaches another technique called an information display system. According to this technique, a camera and/or a radar is provided in a front side of an own vehicle. Visual image, which indicates a state of a road ahead of the own vehicle, and/or information, which is about a preceding vehicle ahead of the own vehicle, are obtained through the camera and/or the radar and are displayed on a display device provided in a rear side of the vehicle. In this way, the obtained information is displayed to a vehicle traveling after the own vehicle.
However, in the case of Japanese Unexamined Patent Publication No. 2005-11249, the infrastructure, such as the sensors and the cameras, which collect the information, and the communication devices, which transmit the collected information, are required. In the current state where such an infrastructure is not well established, the above system is not useful. Furthermore, in order to establish the infrastructure at the useful level, the costs are disadvantageously increased. Also, it is required to provide a communication device to the vehicle side in addition to the road side, resulting in the additional costs to the users.
Furthermore, according to Japanese Unexamined Patent Publication No. 10-000989, the information can be obtained only when the camera and the display device are provided in the preceding vehicle. Thus, the availability of the information fully depends on the other vehicles, and the vehicles having the camera and the display device rarely exist. Therefore, the above technique does not provide the sufficient solution against the blind spot caused by the preceding vehicle.